linux-kernel - Re: [PATCH net-next v2] xfrm: Add ESN support for IPSec HW offload

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Message-ID: <b9e24887-ae26-59c2-9ccf-d71c1429c8c9@oracle.com>
Date:   Wed, 10 Jan 2018 09:36:33 -0800
From:   Shannon Nelson <shannon.nelson@...cle.com>
To:     yossefe@...lanox.com, Jonathan Corbet <corbet@....net>,
        "David S. Miller" <davem@...emloft.net>,
        Steffen Klassert <steffen.klassert@...unet.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org
Cc:     borisp@...lanox.com, kliteyn@...lanox.com, yossiku@...lanox.com
Subject: Re: [PATCH net-next v2] xfrm: Add ESN support for IPSec HW offload

On 1/10/2018 2:34 AM, yossefe@...lanox.com wrote:
> From: Yossef Efraim <yossefe@...lanox.com>
> 
> This patch adds ESN support to IPsec device offload.
> Adding new xfrm device operation to synchronize device ESN.
> 
> Signed-off-by: Yossef Efraim <yossefe@...lanox.com>
> ---
> Changes from v1:
>   - Added documentation
> ---
>   Documentation/networking/xfrm_device.txt |  3 +++
>   include/linux/netdevice.h                |  1 +
>   include/net/xfrm.h                       | 12 ++++++++++++
>   net/xfrm/xfrm_device.c                   |  4 ++--
>   net/xfrm/xfrm_replay.c                   |  2 ++
>   5 files changed, 20 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/networking/xfrm_device.txt b/Documentation/networking/xfrm_device.txt
> index 2d9d588c..50c34ca 100644
> --- a/Documentation/networking/xfrm_device.txt
> +++ b/Documentation/networking/xfrm_device.txt
> @@ -41,6 +41,7 @@ struct xfrmdev_ops {
>   	void	(*xdo_dev_state_free) (struct xfrm_state *x);
>   	bool	(*xdo_dev_offload_ok) (struct sk_buff *skb,
>   				       struct xfrm_state *x);
> +	void    (*xdo_dev_state_advance_esn) (struct xfrm_state *x);
>   };
>   
>   The NIC driver offering ipsec offload will need to implement these
> @@ -117,6 +118,8 @@ the stack in xfrm_input().
>   
>   	hand the packet to napi_gro_receive() as usual
>   
> +In ESN mode, xdo_dev_state_advance_esn() is called from xfrm_replay_advance_esn().
> +Driver will check packet seq number and update HW ESN state machine if needed.
>   
>   When the SA is removed by the user, the driver's xdo_dev_state_delete()
>   is asked to disable the offload.  Later, xdo_dev_state_free() is called
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index 352066e..3c81cd7 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -842,6 +842,7 @@ struct xfrmdev_ops {
>   	void	(*xdo_dev_state_free) (struct xfrm_state *x);
>   	bool	(*xdo_dev_offload_ok) (struct sk_buff *skb,
>   				       struct xfrm_state *x);
> +	void	(*xdo_dev_state_advance_esn) (struct xfrm_state *x);
>   };
>   #endif
>   
> diff --git a/include/net/xfrm.h b/include/net/xfrm.h
> index 079ea94..1ca2e6e 100644
> --- a/include/net/xfrm.h
> +++ b/include/net/xfrm.h
> @@ -1901,6 +1901,14 @@ int xfrm_dev_state_add(struct net *net, struct xfrm_state *x,
>   		       struct xfrm_user_offload *xuo);
>   bool xfrm_dev_offload_ok(struct sk_buff *skb, struct xfrm_state *x);
>   
> +static inline void xfrm_dev_state_advance_esn(struct xfrm_state *x)
> +{
> +	struct xfrm_state_offload *xso = &x->xso;
> +
> +	if (xso->dev && xso->dev->xfrmdev_ops->xdo_dev_state_advance_esn)
> +		xso->dev->xfrmdev_ops->xdo_dev_state_advance_esn(x);
> +}
> +
>   static inline bool xfrm_dst_offload_ok(struct dst_entry *dst)
>   {
>   	struct xfrm_state *x = dst->xfrm;
> @@ -1971,6 +1979,10 @@ static inline bool xfrm_dev_offload_ok(struct sk_buff *skb, struct xfrm_state *x
>   	return false;
>   }
>   
> +static inline void xfrm_dev_state_advance_esn(struct xfrm_state *x)
> +{
> +}
> +
>   static inline bool xfrm_dst_offload_ok(struct dst_entry *dst)
>   {
>   	return false;
> diff --git a/net/xfrm/xfrm_device.c b/net/xfrm/xfrm_device.c
> index 7598250..704a055 100644
> --- a/net/xfrm/xfrm_device.c
> +++ b/net/xfrm/xfrm_device.c
> @@ -147,8 +147,8 @@ int xfrm_dev_state_add(struct net *net, struct xfrm_state *x,
>   	if (!x->type_offload)
>   		return -EINVAL;
>   
> -	/* We don't yet support UDP encapsulation, TFC padding and ESN. */
> -	if (x->encap || x->tfcpad || (x->props.flags & XFRM_STATE_ESN))
> +	/* We don't yet support UDP encapsulation and TFC padding. */
> +	if (x->encap || x->tfcpad)

As I mentioned before, this will cause issues when working with hardware 
that has no ESN support, such as Intel's x540: the stack will expect the 
driver to do ESN, and nothing actually happens but a rollover of the 
numbers.  Sure, the driver could look for the ESN attribute and fail the 
add, but that's a mode where we have to update every driver to fend off 
problems every time we add a new feature.  Much better is to only update 
drivers that actively support the new feature.

Look at how feature bits are added to netdev->features to signify what 
the driver can do.  I think that's a much better approach.

sln


>   		return -EINVAL;
>   
>   	dev = dev_get_by_index(net, xuo->ifindex);
> diff --git a/net/xfrm/xfrm_replay.c b/net/xfrm/xfrm_replay.c
> index 0250181..1d38c6a 100644
> --- a/net/xfrm/xfrm_replay.c
> +++ b/net/xfrm/xfrm_replay.c
> @@ -551,6 +551,8 @@ static void xfrm_replay_advance_esn(struct xfrm_state *x, __be32 net_seq)
>   			bitnr = replay_esn->replay_window - (diff - pos);
>   	}
>   
> +	xfrm_dev_state_advance_esn(x);
> +
>   	nr = bitnr >> 5;
>   	bitnr = bitnr & 0x1F;
>   	replay_esn->bmp[nr] |= (1U << bitnr);
>